Modern electronic equipments often require driver circuits for operating pairs of complementary output transistors. For instance, solid state, high power, audio frequency amplifiers usually include a pair of complementary discrete power transistors for driving a load such as a loud speaker. A driver circuit is generally coupled from a source of input signals to the complementary power transistors and a bias network associated with them. In some instances, it is desirable for the driver circuit to be manufactured in monolithic integrated circuit form to facilitate low cost, minimum space and maximum reliability. Such monolithic driver circuits are required to provide a quiescent current of a known magnitude for operating the bias network which can be located external to the integrated circuits and which biases the complementary pair for Class "AB" operation. Also, such monolithic circuits must provide drive signals of sufficient magnitude to operate the complementary transistors over a specified dynamic signal range.
Most discrete driver circuits for complementary output transistors are operated in the Class "A" mode. If such circuits are integrated and placed in standard packages, their power dissipation requirements would undesirably limit the amount of drive power available to the complementary output transistors. In particular, Class "A" drivers have poor efficiency because the magnitude of the quiescent current through the Class "A" circuit must approximate the magnitude of the current necessary to drive the complementary power transistors at the maximum output current. The large amount of current constantly required by Class "A" drivers under quiescent conditions would tend to undesirably cause heating of the integrated circuit chip and to undesirably load the power supply. In addition, most N-epi integrated circuits utilize PNP current sources which are not individually capable of supplying the amount of current demanded by Class "A" driver circuits. If such current sources were paralleled to meet the demand, they would take up an undesirable amount of valuable chip surface area.
Consequently, Class "B" power driver circuits have been developed for maximizing power to the complementary transistors during dynamic operation while minimizing the amount of power dissipated by the integrated circuit during quiescent operation. Some prior art Class "B" driver circuits tend to produce second harmonic or crossover distortion in the output signals because of unequal signal gains in each of the paths running from the signal supply to the control electrodes of each of the complementary output transistors. Furthermore, prior art Class "B" drive circuits tend to have temperature stability problems. Also, prior art Class "B" driver circuits sometimes themselves require a differential drive and thus are not suitable for being used directly with circuits providing only a single-ended drive signal. A further problem associated with some prior art complementary driver circuits relates to their inability to provide quiescent output currents of predetermined magnitudes for powering the bias networks associated with the complementary output transistors.